The development of fly ash and incinerated paper sludge ash blend as a source material for preparing geopolymer concrete is presented in the paper. The specimens were prepared with varying percentage of fly ash replaced by paper sludge ash under different curing regimes. The compressive strength, splitting tensile strength, and bending strength values were tested and geopolymer microstructure was analysed. The up to 10% increase in strength of geopolymer concrete containing fly ash and paper sludge ash shows that good prospects exist for the use of this type of concrete for cast-in-situ applications.